Power-factor control for power distribution



Aug. 14, 1928.

' s. MELTON POWER FACTOR CONTROL FOR POWER DISTRIBUTION Original Filed NOV.` 10, 1925 o HN bbb

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WN. Y RMK Jamoc( asilo/f INVENTOR hcman Mah/027,

2f, ATTORNEYS f tems.

' Patented Aug. i4, 192s.

UNITEDl STATES PATENT oFFici-i.

SHERMAN MELTON, or sTUaGIs, xENTUcxY.

Pownizfrnc'roa coNTaoL ron Powna DISTRIBUTION..

Original application led November 10,1925, Serial No. 468,219.` Divided and this application filed .Tune 9,

' 1926. Serial No. 114,770.

This invention relates to a power factor control system for power distribution sys- The presentV application is a division of ending application `Serial No'. 68,219 filed ovember 10, 1925. v

lIn power transmission and distribution systems synchronous motors are commonly employed for driving direct current generators, the synchronous motors being con*- nec'ted to the alternating current power4 lines and the direct current generators supplying currrent for distribution. In systemsof this character the power factor of the. alterpat during li ht loady periods' and lag uring heavy load periods. This condition is due to the synchronous motors and unless corrected, results in vlow operating elciency ofthe sys- Thepresent invention relates particularlyV to a system wherein several direct current generators are driven by a synchronous motor and it is desired to maintain 'the 2 5 power factor of the alternating current aowhereby the above `advantages may ac'- power system, to which the synchronous:

motor is connected, tft unity'. The purposeof the present 'invention 1s lto provide automatic regulating means complished.

Beferr'ing toV the accompanying vdrawingv l the 'iigure represents diagrammatically a s hronous alternating current motor for raving several direct current generators andasingle field exciter, and certain connec ations .whereby the present invention maybe practiced.

Referring to the' drawing more particu- "larly 10 indicates an alternating current synchronous motor which may be connected to a three phase alternating current supply cables or wires-*11 extended from4 a power plant. The-motor 10 may drive the'directj current generators lindicated at 12, 13,"14

50l series coil 18., The shunt field is providedv and 15 and a direct current exciter indicated 'at 1e. l

The exciter 16 may `have .a compound field comprising the usual shunt coil 17 and a with a rheostat 19. The generators 13, A14: and 15 are provided with fields 21, 22 and 23 respectively. Each field A21, 22 and. 23 is' provided with an adjustable resistance 24.

The fields 21, 22 and 23 are ,connected parallel with each other and all connected 1n series with the armature' of exciterl',

and also in series withthe field coil 25 of the generator 12.l The coil `25 of generator 12 may Abe s hunted by a resistance -26 if desire Y.

The synchronous motor 10 lhas its field coils 27 connected. in series with the arma- I `is preferably provided with an adjustablefresistance 80.

In the operation lof ithe present. system,

strengthening of the vauxiliary eldsofthe creases the voltage of .the generator 12 with respect to theexciter 16 and field of syn` chronous motor.' The increase ofvoltage at output-terminals of\, enerator or .booster 12 in turn strengthens lt e field of the'synchro'- .generators 13,-14'and 15 correspondingly innous motor 10 and eonsequently causessaid motor to develops. greater counter'l electro motive force w ich acts to maintain the power factor of the power system, to 'which the motorv 10 is connected, at approximately It will be noted that the voltage ofthe ex' citer roper in circuits of this character, is inten ed to remain continuous and therefore I do not vary the voltage of the main exciter but do vary the voltage, acrossthe terminals of the synchronous motor v'field circuit by adding the voltage generated on the motor eld circuit. Since the added voltage tothe syn ronous motor the power factor vdirect current generator 12 to the voltage already being applied tothe synchronous` may be maintained at a predetermined value and may be caused toincrease to lead with an increase in the load, or may cause the leading one. vThese variations vmay be acpower factor to change from a lagging to a complished by changingthe' resistance of the vfield circuits 25 .and 27 for the direct current generator 12 and synchronous motor field Ycircuits respectively.

What Iy claim is; l L 1. 'In asystem 'of the character described, a synchronous motor driving a pluralityof generators 'and anexciter, means whereby the exciter mayfbe utilized for controlling the field of said generators, means whereby van increase of current from said exciter will v1n direct proportion raise the output voltage of one of said generators, and connecting means whereby the last named generator will supply the field current ofrsaid synchronous motor. v

2. In a system of the character described, a synchronous motor, a plurality of direct current generators and a direct current i'ield exciter driven by said synchronous motor, means whereby the exciter will control the fields vof said generators', ,connecting means whereby the output current of the exciter will flow through a field coil of one ofthe generatorsfand means whereby the last named generator will supply the field of the lcurrent generators and a direct current field exciter driven by the synchronous motor, l

connecting means whereby the output cur rent of the exciter will flow through a ield coil of one of the generators, means for supplying a field coil of each of the remaining generators from the exciter, and means 'for connecting the field of the synchronous motor to the generator having a ield lconnected in series with the output terminals'of the exciter.

SHERMAN MELTON. 

